1. Field of the Invention
The present invention relates to industrial fans, such as industrial ceiling fans and, in particular, involves a safety system that inhibits the fan from falling as a result of motor shaft failure.
2. Description of the Related Art
Fans are commonly used appliances for cooling the interiors of buildings. In some industrial applications, very large fans with blades having diameters in excess of ten feet are often used to cool the interior of buildings. In some industrial applications, it is not possible or cost effective to run air conditioning systems and, in these circumstances, large fans that produce a substantial air flow can significantly reduce the ambient air temperature inside the building.
One example of the type of building that would use a fan for cooling purposes rather than an air conditioning system would be a shop-type building where welding or other fabrication is going on. In this environment, there can be a large amount of smoke or particulate air pollution necessitating constant access to fresh air for the workers therein. To achieve this, either a highly expensive air exchange system would have to be installed on the building or, more commonly, the doors and windows of the buildings are left open to provide venting for the smoke and gas by-products of the welding processes. Air exchange systems are often very expensive, but, in many locations, leaving the doors and windows open is also uncomfortable. For example, in hot weather, the inside of the building may become uncomfortably hot. To address this, fans, including large fans such as those described in U.S. Pat. No. 6,224,821 may be used to set up an airflow within the building to achieve greater cooling.
While these fans provide improved low-cost cooling within the building, it also must be recognized that these fans pose a potential hazard. Specifically, if the shaft of the motor of the fan should break or if the fan blades are hubs otherwise disengage from the shaft, the spinning fan blade could conceivably fall onto the workspace floor and potentially injure people. This problem can be exacerbated by the large size of the fans in question. As described in the U.S. Pat. No. 6,244,821, larger sized fans can produce a greater volume of moving air. These fans can have fan blades with a diameter approaching 20 feet. As such, these fans are relatively heavy and occupy a large amount of space which increases the risk to individuals working in the building should the fans fall from a ceiling mount location.
To address this particular problem, the design disclosed in the U.S. Pat. No. 6,244,821 included a lip formed on the hub that engaged with a plate formed on the motor mount. The lip will preferably catch on the plate when the motor shaft breaks thereby inhibiting the fan blade assembly from falling to the floor. While this implementation works well in the configuration of fans illustrated in the '821 patent, new designs of fans with increased numbers of blades make it more difficult to form lips on the hub that could engage a mounting assembly on the motor mount.
Hence, from the foregoing, it will be apparent that there is a need for an improved safety system that will inhibit fan blade assemblies from falling to the ground when the motor shaft of a fan motor breaks or the hub otherwise disengages from the shaft. To this end, there is a need for a more compact securing system that could be used with hub and fan assemblies that have multiple blades.